Angiotensin II, bradykinin, and vasopressin stimulate PGE2 biosynthesis in the rabbit renomedullary interstitial cell in tissue culture. Hormonal stimulation of PGE2 biosynthesis is mediated by phospholipase activation and can be inhibited by mepacrine. Hormonal stimulation of PGE2 biosynthesis is dependent upon protein synthesis and can be inhibited by inhibitors of protein synthesis, such as cycloheximide. A similar pathway for vasopressin-stimulated PGE biosynthesis was found in the toad urinary bladder where vasopressin-stimulated PGE biosynthesis inhibits vasopressin-stimulated water flow. PGE biosynthesis in the toad urinary bladder is inhibited by the sulfonylureas, which enhance vasopressin-stimulated water flow. In studies of normal man it was found that ACTH and prostaglandin synthesis inhibition interact to produce inappropriate anti-diuresis by an unknown mechanism. BIBLIOGRAPHIC REFERENCES: Zusman, R.M., and Keiser, H.R.: Prostaglandin biosynthesis by rabbit renomedullary interstitial cells in tissue culture: Stimulation by angiotensin II, bradykinin, and arginine vasopressin. Journal of Clinical Investigation 60: 215-223, 1977. Zusman, R.M., and Keiser, H.R. Prostaglandin E2 biosynthesis by rabbit renomedullary interstitial cells in tissue culture: Mechanism of stimulation by angiotensin II, bradykinin, and arginine vasopressin. Journal of Biological Chemistry 252: 2069-2071, 1977.